As Rust is a young language containing many innovative features, questions about how to structure Rust libraries and API's are common. Heavy use of metaprogramming and trait constraints can make libraries hard to understand and use, but also bring great power to reason about programs at compile-time. How do you design a library that exploits the power of Rust without making new users say 'This is way too complicated to bother with'? We will discuss these issues using an existing Rust crate as a case study in both designing an API and how it is influenced by the API decisions of the crates it uses as dependencies.